The present invention relates to a process for the preparation of a starting material for the subsequent production of a fibre-reinforced plastics moulding, a starting material prepared by the process and a plastics moulding produced from the starting material.
The article entitled: xe2x80x9cWerkstoffe im Automobilbauxe2x80x9d [Materials in automotive construction] in the German newspaper: Sonderausgabe der Automobiltechnische Zeitung (ATZ) [Special issue of the Automotive Newspaper] discloses a fibre-reinforced plastics moulding which is formed from a plastics matrix and from natural fibres which are embedded in the plastics matrix. To ensure good disposal of the plastics moulding, the plastics matrix consists of so-called biopolymers, which are natural, organic macromolecules and are obtained from renewable raw materials, such as sugar beets, potatoes, maize or cellulose (including wastepaper). Natural fibres are defined as those fibres which are obtained as renewable raw materials in nature. Plastics mouldings formed in this manner are safely biodegraded on disposal since all their organic constituents rot and are converted into water, CO2, humus and biomass as well as bacteria and moulds in the rotting cycle, the CO2 formed during the rotting being neutral in the ecological balance since it was in fact previously withdrawn from the atmosphere by the renewable raw materials.
Plastics in which pliable or flexible fibres, in particular natural fibres, are incorporated in a plastics matrix comprising synthetic and/or biological polymers generally have a poor distribution of the fibres, i.e. the fibres are generally bundled and have a poor random uniform distribution. Because of this in turn, the stability of these plastics mouldings is very low. Furthermore, owing to the damage to the fibres during shaping, the average fibre length is also very limited.
It is the object of the invention to provide a process for the preparation of a starting material with which, in a shaping process known per se, such as injection moulding, pressure die-casting, flow moulding and the like, it is subsequently possible to produce economical plastics mouldings having pliable fibres, in particular natural fibres, incorporated in a plastics matrix, the stability of which mouldings is improved. Furthermore, it is the object of the invention to propose a starting material and a corresponding plastics moulding.
The object is achieved by a process according to the present invention. As a result of the dry-blending of the polymer or of the polymers and of the pliable fibres to give a solids mixture and the subsequent at least partial embedding of the fibres in the heated polymer or the heated polymers, the fibres are to a high degree thinly and randomly uniformly distributed in the starting material. Furthermore, in the case of the starting material according to the invention and also in the case of a plastics moulding produced therefrom, the average fibre length is longer compared with mouldings to date. If a moulding is produced from such a starting material by, for example, injection moulding or compression moulding, the corresponding moulding then also has the fibres distributed singly and very uniformly, with the result that a moulding having good mechanical properties can be produced in an economical manner. Furthermore, in the invention, the proportion of ecologically harmful substances is reduced compared with comparable mouldings of purely synthetic substances by the use of natural fibres.
Further advantageous embodiments of the invention are described in the respective subclaims. Otherwise, the invention is illustrated in more detail with reference to embodiments shown in the figures and six exemplary examples.